Engine remote control system

ABSTRACT

Disclosed is a remote control system which produces electric signals to be sent to a governor driving device from an operator&#39;s cabin for remote control of the governor mechanism. This remote control system essentially includes a detector for detecting the amount of control effected to the governor mechanism, and a control device which operates on detection signals from the detector and operation signals from an operating device in the operator&#39;s cabin. The control device is adapted to produce a stop signal to the driving device when the difference in control amount between two cyclic time points becomes smaller than a predetermined value, which is regarded as a limit of operation of the governor mechanism, thereby preventing impairment or damages of the governor mechanism and operating device.

FIELD OF THE ART

This invention relates to an engine remote control system particularlysuitable, for example, for remote control of a governor mechanism ofDiesel engine on a construction machine.

BACKGROUND OF THE ART

Construction machines such as hydraulic cranes, power shovels and thelike generally have a Diesel engine mounted thereon as a power sourcefor rotationally driving a hydraulic pump or pumps.

Heretofore, it has been the conventional practice to provide an enginecontrol lever in the driver's cabin of a construction machine,connecting the engine control lever to an engine governor mechanismthrough a control cable, link rod or the like for engine control.However, such a control cable or link rod which mechanically connectsthe control lever to the governor mechanism involves a great deal ofmechanical resistance which will require a large operating force inaddition to a problem of low response characteristics.

In an attempt to improve these drawbacks, there has been proposed asystem for electrically remote-controlling the engine governor mechanism(Japanese Laid-Open Utility Model Application 61-145849), the remotecontrol system being provided with: a governor adjusting driving deviceincluding an electric motor and located in the vicinity of the engine;an adjustment sensor for detecting the extent of actually effectedadjustment in terms of the rotational angle of the electric motor outputshaft of the driving device; an operating device provided in theoperator's cabin and adapted to produce a command signal commensuratewith the extent of manipulation of an operation switch or otheroperating means; and a control device like a microcomputer adapted tocontrol the rotation of the electric motor of the drive means on thebasis of the detection signal from the adjustment sensor and the commandsignal from the operating device in such a manner as to zeroize thedifference between the two signals.

With this arrangement, the control lever of the governor mechanism isturned to an extent corresponding to the extent of manipulation of theoperating means through feedback control of the driving device, whichzeroizes the difference between the above-mentioned detection andcommand signals.

However, the above-mentioned engine remote control system, which isarranged to turn the control lever of the governor mechanism into atilted position by controlling the rotation of the electric motor of thedriving device, needs to provide means for preventing impairment orbreakage of the electric motor or control lever which might result fromoverrunning rotation of the electric motor.

Therefore, for the purpose of delimiting the rotational angle (operatingrange) of the electric motor, the prior art systems are usually providedwith a couple of limit switches and a cam member on the output shaft ofthe electric motor.

Naturally, the system construction including such limit switches and acam member requires an increased number of component parts, and accuratepreadjustments of operating points of the respective component parts,which are very troublesome.

Further, for the feedback control of the electric motor, the prior artsystem is arranged to compare the command signal from the operatingdevice with the detection signal from the adjustment sensor whichdetects the rotational angle of the electric motor, so that there arisesa necessity for preadjustments to bring the output range of the commandsignals from the operating device into conformity with the detectionrange of the adjustment detector, making the operations for adjustmentsof actual variations extremely difficult.

The present invention contemplates to eliminate the above-mentioneddrawbacks of the prior art system, and has as its object the provisionof an engine remote control system which is adapted to actuate anddeactuate a driving device in relation with variations in the degree oftilting of the governor mechanism which is checked up in each programcycle, obviating the use of limit switches and a cam which have beenconventionally resorted to for detection of the limits of the rotationalangle of the driving device and unnecessitating the interrelatingpreadjustments of the operating and detecting devices.

DISCLOSURE OF THE INVENTION

In order to achieve the above-mentioned objectives, the engine remotecontrol system of the invention includes: an engine having a governormechanism for controlling the output rotation of the engine according toa specified control amount; a driving device for driving the enginegovernor mechanism; a detector for discerning the extent of controleffected to the governor mechanism by the driving device; an operatingdevice for producing an operation signal for controlling the outputrotation of the engine; and a control device for producing a drivesignal or a stop signal to the driving device on the basis of theoperation signal from the operating device and the detection signal fromthe detector, the control device being adapted to read in the detectionsignal cyclically at predetermined time intervals, and compare theextent of effected control in a current cycle of surveillance with theextent of effected control in a preceding cycle to produce a stop signalto the driving device when the difference between the two cycles becomessmaller than a predetermined value, otherwise producing a drive signalbased on the operation signal.

With this arrangement, the tilted condition of the governor mechanism ischecked by way of the detection signal from the detector atpredetermined time intervals determined by a program cycle, while thedegree of effected control in a cycle of surveillance is compared withthe degree of effected control in a preceding cycle to check if thegovernor mechanism has reached a limit of its operation. It follows thatthe driving device can be stopped as soon as the governor mechanismreaches its operation limit to prevent damages which might otherwise becaused to the governor mechanism and driving device.

According to an aspect of the present invention, the control deviceincludes: a first drive control means adapted to read in the detectionsignal cyclically at predetermined time intervals, and compare theextent of effected control in a given cycle of surveillance with thedegree of effected control in a preceding cycle, producing a stop signalto the driving device when the difference between the two cycles becomessmaller than a predetermined value regarded as a limit of operation ofthe governor mechanism, otherwise producing a drive signal based on theoperation signal from the operating device; a memory means with afunction of learning and storing as a control limit the degree ofeffected control at a time point when an operation limit of the governormechanism is discriminated by the first drive control means; and asecond drive control means adapted to compare the control limit storedin the memory means with a detected degree of control from the sensor inthe cycles succeeding the discrimination of the control limit of thegovernor mechanism and to produce a stop signal to the driving devicewhen the difference is smaller than a predetermined value regarded as alimit of operation of the governor mechanism, otherwise producing adrive signal based on the operation signal.

With this arrangement, when the governor mechanism is judged by thefirst drive control means as having reached a limit of its operation,the maximum or minimum degree of control at that time point is learnedand stored by the memory means. Thereafter, the driving device can bestopped on the basis of the control limit stored in the memory and thedetected degree of control from the detector, permitting high precisioncontrol even against variations in characteristics of the respectivedevices over an extended time period.

If desired, a protection device may be provided between the drivingdevice and governor mechanism for permitting free action of the drivingdevice when the driving force to be applied to the governor mechanismexceeds a certain predetermined level.

The provision of such a protection device contributes to stabilize theoperation control even in the event when operation errors occur to thedriving device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1 to 3 show an embodiment of the invention, of which,

FIG. 1 is a schematic illustration of the layout of an engine remotecontrol system according to the invention;

FIG. 2 is a diagrammatic illustration of the construction of a memoryarea provided in the control device; and

FIG. 3 is a flow chart of processing steps executed by the controldevice for the control of the driving device;

FIG. 4 is a flow chart of processing steps for the control of thedriving device in another embodiment of the invention; and

FIGS. 5 and 6 show still another embodiment of the invention, of which,

FIG. 5 is a schematic illustration of the layout of an engine remotecontrol system in a third embodiment; and

FIG. 6 is a schematic outer view showing on an enlarged scale aprotection device shown in FIG. 5.

BEST MODE FOR PRACTICING THE INVENTION

Hereafter, the invention is described more particularly by way of thepreferred embodiments shown in the accompanying drawings.

Referring to FIGS. 1 to 3, there is shown a first embodiment of theinvention. In FIG. 1, indicated at 1 is a Diesel engine (hereinafterreferred to simply as "engine" for brevity) which is mounted on aconstruction machine. The engine 1 is provided with a governor mechanism2 with a control lever 3 to adjust the engine speed according to thedegree of tilting of the control lever 3 in an accelerating direction Hor in a decelerating direction L. Denoted at 4 and 5 are stoppers whichlimit the rotation of the control lever 3 in the accelerating anddecelerating directions, respectively.

The reference numeral 6 indicates a driving device which is provided inthe vicinity of the engine 1 and consists of a reversible steppingmotor, brushless DC motor or the like. A lever 6A which is mounted onthe output shaft of the motor 6 is connected to the control lever 3 by alink 7, so that the control lever 3 is tilted into the acceleratingdirection H or decelerating direction L according to the forward orreverse rotation of the drive mechanism 6. Even when a stop signal isapplied to the driving device 6 to stop its rotation, the control lever3 can be maintained at a tilted angle corresponding to an operationsignal from an operating device 10, which will be described hereinafter,to hold the engine 1 in operation at constant speed.

Designated at 8 is a detector, for example, a rotational angle sensorlike rotary encoder, which is located in the vicinity of the engine 1and has a lever 8A mounted on its rotational shaft. The lever 8A isconnected to the control lever 3 through a link 9 to produce a detectionsignal in the form of a detection voltage or digital signalcorresponding to the degree of tilting of the control lever 3.

The afore-mentioned operating device 10 is provided in an operator'scabin of construction machine for setting the rotational speed of theengine 1 in the accelerating or decelerating direction. For example, asthe operating device, there may be employed a rotary switch or the likewhich is operationally interlocked with an up-down switch orpotentiometer to produce an accelerating or decelerating operationsignal corresponding to the extent of manipulation of the operatingdevice for supply through signal lines 11 and 12 to a control device 13which will be described hereinafter. In case an up-down switch is usedas the operating device, settings of acceleration and deceleration aremade while the up- and down-switches are depressed, respectively.

Designated at 13 is the control device which is provided, for example,in a control unit in the operator's cabin, and constituted by amicrocomputer including processing circuits composed of CPU, MPU and thelike, a memory circuit composed of ROM, RAM and the like, and an I/Ocontrol circuit. The input side of the control device 13 is connected tothe operating device 10 through the signal lines 11 and 12, and to thedetector 8 through signal line 14, while its output side is connected tothe driving device 6 through signal line 15.

In this instance, the memory circuit of the control device 13 isprovided with a memory area 16 as shown in FIG. 2, and stores a programshown in FIG. 3 and executed as will be described hereinafter forcontrolling the drive and stop of the driving device 6.

The memory area 16 includes areas 16A to 16J. Namely, the area 16Aserves to store an acceleration limit flag H indicative of a state ofthe control lever 3 which is judged to have reached an accelerationlimit position abutting against the stopper 4; and the area 16Bsimilarly serves to store a deceleration limit flag L indicative of astate of the control lever 3 which is judged to have reached adeceleration limit position abutting against the stopper 5. The area 16Cis provided for realizing a counter N. The area 16D serves to store acurrent detection voltage E_(n) read in a current program cycle, whilethe area 16E serves to store a previous detection voltage E_(N--1) readin a previous program cycle. The area 16F serves to store a stop callvoltage k, e.g. k=2V, requiring stoppage of the driving device 6 becauseof the control lever 3 of the governor 2 reaching its operation limit,and the area 16G similarly serves to store a stop call voltage j, e.g.j=2V. Further, the area 16H serves to store, as an acceleration limitvoltage E_(H), the voltage which is detected when the acceleration limitflag H turns to "1" in the processing of the second embodiment whichwill be described hereinafter, and renews its content by programmedlearning every time when the engine is started. The area 16I stores adeceleration limit voltage E_(L) similarly in the processing of thesecond embodiment, renewing its content by programmed learning. The area16J stores a hysteresis time t_(o), e.g., t_(o) =1 second, inconsideration of the hysteresis of a potentiometer or the like by thetime lag of producing an operation signal to be actually set up afterturning on a switch of the operating device 10.

Now, reference is had to FIG. 3 for explanation of the operation of thefirst embodiment, which is arranged in the above-described manner.

Firstly, upon starting the processing by turning on the engine key, thecontrol device 13 initializes the acceleration and deceleration limitflags H and L to "0" under control of the processing circuit (step S1).Nextly, the control device 13 reads in the operation signal from theoperating device 10 (step S2), and a check is made at step S3 to seewhether or not the up-down switch is ON. If the answer at step S3 is"NO", which means no operation signal is received at the input, controlreturns to step S2 through steps S14 and S16 to carry out a startsurveillance.

On the other hand, the answer in step S3 is "YES", indicating that anoperation signal has been received from the operating device 10, theprocessing proceeds to step S4 to check if the operation signal is ofacceleration or deceleration. When discriminated as of an acceleratingoperation, the deceleration limit flag L is set to "0" at the next stepS5. The deceleration limit flag L is set to "0" at step S5 at the timeof an accelerating operation because under certain circumstances theflag L is set in "1" at step S24 of the deceleration processing routine.

After the processing at step S5, the control proceeds to step S6 tocheck whether or not the acceleration limit flag H is set to "1". If theflag H is "1", it means that the control lever 3 of the governormechanism 2 is in an acceleration limit position abutting against thestopper 4 as will be described hereinafter, and that a further operationof the driving device 6 might damage the driving device 6 and thecontrol lever 2. Therefore, in such a case, the control proceeds fromstep S6 to S14 to produce a stop signal to the driving device 6, holdingthe control lever 3 in the full speed position.

On the other hand, when the acceleration limit flag H is found to be "0"at step S6, the processing proceeds to step S7 to check whether or not apredetermined hysteresis time t_(o) has lapsed after turning on theswitch of the operating device 10. If "NO", control goes to step S15 toproduce a drive signal. Step S7 is executed only in the initial programcycle, in consideration of the hysteresis which occurs to thepotentiometer or the like as mentioned hereinbefore due to the time gapbetween the turning-on of the switch of the operating device 10 and theproduction of an operation signal to be actually set up.

If the execution of step S7 results in "YES", which means that theproblem of hysteresis has been solved, control advances to step S8 toincrement the counter N of the area 16C, reading in the amount of thecurrent detection signal from the detector 8 at next step S9. Then, atstep S10 a detection voltage E_(N) corresponding to the amount of thecurrent detection signal is stored in the area 16D. At the time ofreturning the program cycle, the current detection voltage E_(N) storedin the area 16D may be shifted into the area 16E as a previous detectionvoltage E_(N--1).

Nextly at step S11 a check is made to see whether or not the differencebetween the currently read-in detection voltage E_(N) and the detectionvoltage E_(N--1) read in the previous program cycle is smaller than astop call voltage k. If the answer at step S11 is negative, meaning thatthe control lever 3 of the governor mechanism 2 is being continuallytilted in the accelerating direction, the processing goes to step S15 toproduce to the drive mechanism 6 a drive signal corresponding to theoperation signal, further tilting the control lever 3 in theaccelerating direction by the driving device 6.

When the execution of step S11 results in "YES", this means that thecontrol lever 3 is in a full speed position (maximally tilted position)abutting against the stopper 4, and that the difference between thecurrent detection voltage E_(N) and the previous detection voltageE_(N--1) is smaller than the stop call voltage k. Accordingly, in thiscase the processing proceeds to step S12 to set the acceleration limitflag H in "1", and then to step S13 to produce a stop signal to thedriving device 6, holding the control lever 3 of the governor mechanismat the full speed position

The foregoing operations are performed when step S4 discriminates anaccelerating operation through the operating device 10. In case step S4discriminates a decelerating operation, steps S17 to S27 are executed ina similar manner. When the execution of step S23 results in "YES", thecontrol lever 3 is in an idling speed position (minimally tiltedposition) in abutting engagement with the stopper 5, and a furtherreduction of speed might invite an engine stall (engine stop).Therefore, in such a case control goes to step S24 to set thedeceleration limit flag to "1", and then to step S25 to produce a stopsignal to the driving device 6, holding the control lever 3 in theidling speed position.

Thus, according to the present invention, the difference between thedetection voltages in the previous and current program cycles iscompared with the stop call voltage k in the respective program cyclesat regular time intervals, suspending the application to the drivingdevice 6 of the output drive signal of the control device 13 when theacceleration limit voltage E_(H) or deceleration limit voltage E_(L) isreached, and holding the control lever 3 of the governor mechanism 2 inthe full speed position or in the idling speed position. Accordingly, itbecomes possible to prevent damage and breakage of the driving device 6and control lever 3 without providing limit switches. Besides, stableoperating conditions can be secured without interrelationalpreadjustments in operational or rotational amount of the operatingdevice 10, detector 8, driving device 6, control lever 3 and the like.

Referring now to FIG. 4, there is shown a flow chart in a secondembodiment of the invention, which differs from the first embodiment inthat steps S42, S44, S45, S56, S58 and S59 are added while steps S5 andS17 of FIG. 3 are excluded. This embodiment uses the areas 16H and 16Iof FIG. 2.

Namely, a feature of this embodiment resides in that the accelerationand deceleration limit voltages E_(H) and E_(L) at the time point whenthe operation limit flag H or L turns to "1" are learned and stored inthe memory area every time on an engine start, thereafter producing thedrive and stop signals on the basis of the limit voltages E_(H) andE_(L).

In FIG. 4, after initializing the flags L and H in step S31 at theoutset of processing, the operation signal from the operating device 10is read in at steps S32 and S33. When an accelerating operation isdiscriminated at step S34, the processing proceeds to S35→S36→S47 in theinitial program cycle alone in the same manner as in the firstembodiment, and in the succeeding program cycles to S35→S36→S37→S38→S39→S40→S47 to produce a drive signal to the driving device 6 thereby toaccelerate the speed of the engine 1. When a full speed condition isdiscriminated at step S40 in a certain program cycle, the processinggoes to step S41 to set the acceleration limit flag H to "1". Thisprocessing operation is one particular example of the first drivecontrol means.

When the flag H is set to "1", the detection voltage E at that timepoint is stored in the area 16H as an acceleration limit voltage E_(H),and a stop signal is produced to the driving device 6 at step S40 tohold the control lever 3 of the governor mechanism 2 in the full speedposition, then returning to step S32 from step S48. This process is aparticular example of the memory means.

Therefore, although the above-described process has no difference fromthe first embodiment except that the acceleration limit voltage E_(H) islearned and stored in step S42.

After setting the flag H to "1", the answer in step S35 is always "YES",so that the processing advances to step S34→S35→S44→S45→when anaccelerating operation is discriminated in step S34. At step S45, acheck is made to see whether or not the difference between the currentdetection voltage E according to the detection signal read in at stepS44 and the learned acceleration limit voltage E_(H) is greater than thestop call voltage j. In case the execution of step S45 results in "NO",it means that the control lever 3 of the governor mechanism 2 is beingcontinually turned in the accelerating direction, so that a drive signalcorresponding to the operation signal is produced to the driving device6 in step S47 to further tilt the control lever 3 in the acceleratingdirection through the driving device 6.

In case the answer at step S45 is "YES", the control lever 3 is in thefull speed position abutted against the stopper 4, so that control goesto step S46 to produce a stop signal to the driving device 6, holdingthe full speed position.

On the other hand, when a decelerating operation is discriminated atstep S34, control goes to steps S49-S61, and, when the engine issimilarly found to be at the minimum idling speed in step S54, thedeceleration limit flag L is set to "1" at step S55, while thedeceleration limit voltage E_(L) is stored in the area 16I as a learnedvalue. Thereafter, from step S49 the processing goes to steps S58-S61.This process is a particular example of the second drive control means.

Thus, in this embodiment, the limit voltage E_(H) or E_(L) at the timeof the first full speed rotation or minimum speed idling rotation afteran engine start is stored as a learned value, and thereafter the driveand stop signals are produced on the basis of these limit voltages E_(H)and E_(L), making it possible to effect the remote control appropriatelyin spite of time-wise variations in characteristics and accuracy of theengine 1, driving device 6, detector 8 and so forth. The above-describedlearning processing may be carried out every n-number of times of enginestart, or at the first engine start in a day, or upon receipt of anexternal command signal.

Referring to FIGS. 5 and 6, there is shown a third embodiment of theinvention, which is provided with a protection device between thedriving device and the governor mechanism and wherein the componentparts common to the above-described first embodiment are designated bycommon reference numerals and their description is omitted to avoidunnecessary repetitions.

In these figures, indicated at 21 is a protection device which isprovided between the control lever 3 of the governor mechanism 2 and thelever 6A of the driving device 6, the protection device 21 including arotational shaft 22, three levers 23, 24, 25 rotatably mounted on therotational shaft 22, a biasing spring 26 provided between the levers 23and 24 and constantly urging projections 23A and 24A of these leversinto abutting engagement with each other, and another biasing spring 27provided between the levers 24 and 25 and constantly urging projections24B and 25A of these levels into abutting engagement with each other.The lever 23 is connected to the lever 6A of the driving device 6through a link 28, while the lever 25 is connected to the control lever3 of the governor mechanism 2 through a link 29.

With this arrangement, when the driving device 6 is in normal condition,a rotational movement of the lever 6A of the driving device 6 istransmitted to the lever 23 by displacement of the link 28, and therotational displacement of the lever 23 is transmitted to the lever 25through the spring 26 or 27 and lever 24 and then to the control lever 3of the governor mechanism 2. Accordingly, the levers 23, 24 and 25 ofthe protection device 21 are operated integrally under normal operatingcondition.

On the other hand, in full-speed rotation with the control lever 3abutted against the stopper 4, even if the driving device 6 tends torotate to an excessive degree in the accelerating direction, the lever23 is pulled against the action of the spring 26 since the lever 25 isblocked against rotation, and the lever 23 alone is turned clockwise topermit free action of the driving device 6.

Conversely, in an engine operation with the control lever 3 abuttedagainst the stopper 5, if the driving device 6 tends to rotate to anexcessive degree in the decelerating directions the levers 23 and 24alone are turned counterclockwise to permit free action of the drivingdevice 6.

Thus, in this embodiment, when the driving force of the driving device 6should exceed the preset forces of the springs 26 and 27, the drivingdevice 6 is freed in action to prevent damages or other accidents whichwould be caused by overloading.

Industrial Applicability

It will be appreciated from the foregoing description that the engineremote control system of the invention is arranged to check thecontrolled amount of the control lever in each program cycle or on timebase, stopping the operation of the driving device when the controllever is found to have reached a limit control amount. Since there is noneed for providing limit switches and a cam member for the drivingoperation, the system can be simplified in construction and obviates theinterrelating preadjustments of the driving device, detector andoperating device, in addition to the advantages such as prolongedservice life and stable remote control.

What is claimed is:
 1. An engine remote control system, comprising:anengine having a governor mechanism for controlling the output rotationof the engine according to a specified control amount; a driving devicefor driving said engine governor mechanism; a detector for cyclicallydiscerning the extent of control effected to said governor mechanism bysaid driving device; an operating device for producing an operationsignal for controlling the output rotation of said engine; and a controldevice for producing a drive signal or a stop signal to said drivingdevice on the basis of said operation signal from said operating deviceand said detection signal from said detector, said control device beingadapted to read in said detection signal cyclically at predeterminedtime intervals, compare the extent of effected control in a currentcycle of surveillance with the extent of effected control in a precedingcycle to produce a stop signal to said driving device when thedifference in the extent of control between the two cycles becomessmaller than a predetermined value, otherwise producing a drive signalbased on said operation signal.
 2. An engine remote control system,comprising:an engine having a governor mechanism for controlling theoutput rotation of an engine according to a specified control amount; adriving device for driving said engine governor mechanism; a detectorfor discerning the extent of control effected to said governor mechanismby said driving device; an operating device for producing an operationsignal for controlling the output rotation of said engine; and a controldevice for producing a drive signal or a stop signal to said drivingdevice on the basis of said operation signal from said operating deviceand said detection signal from said detector, said control device havinga first drive control means adapted to produce a drive signal or a stopsignal to said driving device on the basis of said operation signal fromsaid operating device and said detection signal from said detector, readin said detection signal cyclically at predetermined time intervals, andcompare the extent of effected control in a current cycle ofsurveillance with the extent of effected control in a preceding cycle toproduce a stop signal to said driving device when the difference in theextent of control between the two cycles becomes smaller than apredetermined value, otherwise producing a drive signal based on saidoperation signal, a memory means with a function of learning and storingas a control limit the extent of effected control at a time point whenan operation limit of said governor mechanism is discriminated by saidfirst drive control means, and a second drive control means adapted tocompare said control limit stored in said memory means with a detectedamount of control from said detector in cycles succeeding thediscrimination of the control limit of said governor mechanism andproduce a stop signal to said drive mechanism when the difference issmaller than a predetermined value regarded as a limit of operation ofsaid governor mechanism, otherwise producing a drive signal based onsaid operation signal.
 3. An engine remote control system as defined inclaim 1 or 2, wherein a protection device is provided between said driveand said governor mechanisms for permitting free action of said drivemechanism when the driving force to be applied to said governormechanism from said drive mechanism exceeds a predetermined level.